Nkx 2.9 is a
transcription factor responsible for the formation of the
branchial and visceral motor neuron subtypes of
cranial motor nerves in vertebrates. Nkx 2.9 works together with another transcription factor,
Nkx 2.2, to direct neural progenitor cells to their cell fate.[1]
Gene defects
Cell lineage analysis of Nkx 2.9 and Nkx 2.2 double knockout (deficient) mouse embryos shows that cranial nerve alterations are a result of changes in neuronal progenitor cell fate. The
trigeminal nerve is not affected in the double knockout mouse embryos, indicating that cell fate alteration is limited to the caudal
hindbrain; that Nkx 2.9 and Nkx 2.2 proteins do not play a role in branchial or visceral motor neuron development in the portion of the hindbrain superior to
neuromere 4.[1]
Disturbance of Nkx 2.9 and Nkx 2.2 in mouse embryos results in the total loss of the
spinal accessory and
vagal motor nerves, and a partial loss of the
glossopharyngeal and
facial motor nerves. However, the somatic
hypoglossal and
abducens motor nerves are not disrupted.[1]